the rough rule of thumb.
from about 1964-66 if seatbelts were an option on the front seats in the vehicle you were purchasing they had to be fitted.
from 66-68 you had to have them in the front seats some states only required the outside seats others required all of the front seats to be belted IF seatbelts were an option for the rear in some states they had to be fitted.
post 68 seat belts were mandatory in all seating positions except some types of sideways facing seats. I think but have never been able to confirm that this exemption ceased in the early 70's and was not the intent of the law but it was circumventable if your vehicle could seat more than 10 and be classed as an bus.
In all cases, where a seatbelt was fitted it was mandatory to wear it and have it properly adjusted. The driver was responsible for minors that were in the vehicle (I believe the cut off age was/is 13-15) and both the driver and the passanger not wearing a seatbelt can be fined if a passanger is not wearing a seatbelt. Pregnant women and some religions are permitted to not wear a seat belt, the pregnant woman no matter how obviously pregnant must provide a DR certificate if requested but all some towelhead has to do is advise that it interferes with whatever do gooder hippy spritual sacrament bunch of snot it is that gets them that exemption.
Personally If I see said towel head I am going to head on his car and as he lays there in agony Im going to ask him where is his god now and if he hadn't had his priority's tailendround he might not be on his way to see said deity right about now, Safety first people

